Question: What is the greatest common factor of $2$ and $18$ ? Another way to say this is: $\operatorname{gcf}(2, 18) = {?}$
Solution: The greatest common factor is the largest number that is a factor of both $2$ and $18$ The factors of $2$ are $1$ and $2$ The factors of $18$ are $1$ $2$ $3$ $6$ $9$ , and $18$ Thus, the greatest common factor of $2$ and $18$ is $2$. $\operatorname{gcf}(2, 18) = 2$